1. Field of the Invention
The present invention relates to an imaging element, an imaging device, an endoscope, an endoscope system, and a method of driving an imaging element.
2. Description of the Related Art
In an imaging device including a complementary metal-oxide semiconductor (CMOS) imaging element, power consumption differs between a blanking period and an imaging signal period. Thus in the initial part of the imaging signal period, fluctuation in power consumption causes the power source voltage to fluctuate, which results in distortion of an image.
To suppress such fluctuation in power consumption, provision of a circuit for supplying a current during a period where power consumption is low is proposed (for example, see Japanese Laid-open Patent Publication No. 2008-117304). In the technique disclosed in Japanese Laid-open Patent Publication No. 2008-117304, during a blanking period where the load current in a horizontal transfer circuit decreased to a predetermined threshold value or lower, a load circuit that operates by the same power source for the horizontal transfer circuit supplies a load current that compensates for a decreased amount of load current.
In the technique disclosed in Japanese Laid-open Patent Publication No. 2008-117304, a load circuit is provided to supply a current during a period where power consumption in an imaging element is low, so that a large amount of heat is generated in a chip, degrading the quality of an image under dark circumstances. Thus a conventional technique of providing a load circuit is inappropriate for an application in an endoscope, which is difficult to dissipate heat.
The present invention is made in view of the aforementioned problem. The object of the present invention is to provide an imaging element, an imaging device, an endoscope, and endoscope system, and a method of driving an imaging element that stabilizes a power source voltage and can suppress degradation in image quality.